1. Field of the Invention
The present invention pertains to well tools for retrieving objects from wells. Such tools may be generally referred to as "fishing tools" and the objects to be retrieved as "fish." One particular type of fishing tool to which the invention may be applied is an overshot. Such a tool comprises a plurality of radially movable grapple fingers which may be lowered around the fish, typically a piece of drill pipe or the like, and then contracted inwardly to grip the fish by a surrounding bowl having deflecting surfaces. Another particular type of tool in which the present invention may be incorporated is a spear having similar radial movable slips which may be lowered into a fish, such as a length of casing, and then expanded outwardly to grip the fish by an expander also having deflecting surfaces.
2. Description of the Prior Art
In a prior art fishing tool, the radial movements which are permitted the gripping elements are controlled by relative longitudinal movements of a pair of telescoping assemblies, one of which carries the gripping elements and the other of which carries the deflecting means. Stop surfaces limit these relative movements but can be offset by relative rotation of the assemblies to permit the longitudinal movements. A camming arrangement is provided to selectively align or offset the stop surfaces by converting longitudinal movements of the two assemblies into rotational motion. However, in this tool, the stop surfaces as well as the camming surfaces on at least one of the assemblies are defined by pins or studs which essentially provide only point contact with the corresponding surfaces on the other assembly and which are highly susceptible to shearing and other damage as they strike these surfaces during operation.